The present invention relates to a structure for mounting an instrument such as electric or electronic devices to a body.
The car stereo which is manufactured in a factory is mounted on a frame of an automobile in a factory of an automobile manufacturer. The stereo is mounted directly or through an appropriate holding device on the frame.
Referring to FIG. 5, a car stereo body 3 is inserted in a hole 1 formed in a dashboard of an automobile and mounted on a frame of the dashboard through L-shaped opposite brackets 1a, 1b and 2. The brackets 1a and 1b are secured to opposing inner walls of the hole 1. The brackets 2 are fixed to side panels 3a and 3b of the car stereo body 3 by screws 2b, each of which is screwed in a threaded hole 2a of the bracket 2 and a threaded hole 3c in the panel 3a. A horizontal plate portion of each of the brackets 1a and 1b has a pair of threaded holes 1c at positions corresponding to the threaded holes 2d. The car stereo body 3 is inserted in the hole 1, and the horizontal portions of the brackets 2 are rested on the horizontal portions of the brackets 1b and 1c. The brackets 2 are fixed to the brackets 1b and 1c by screws (not shown) screwed in the threaded holes 2d and 1c. Thus, the car stereo body 3 is securely mounted in the dashboard. Thereafter, a grille 4 is fastened on a front of the car stereo body 3, so that a space formed between the dashboard and the body 3 is covered.
When engaging the screw 2b in the threaded hole 3c of the car stereo body 3, the screw may be incorrectly inserted in the hole 3c. That is, an axis C2 of the screw 2b may be deflected from an axis C1 of the threaded hole 3c by an angle .alpha. as shown in FIG. 6. Since a female screw thread 3e of the threaded hole 3c and a male screw thread 2e of the screw 2b are not properly engaged with each other, the threads are broken when the screw 2b is forced into the hole 3c using a driver 5. Metal chips 6 broken off from the threads are pushed inward by the screw 2b and falls out of the screw hole 3c into the car stereo body 3. The fragments of these chips 6 easily adhere on circuits and other electric devices of the car stereo, thereby causing short circuit, malfunction and breakdown.
In addition, dust and other undesirable foreign substances are apt to accumulate in roots of the threads. As the screw 2b advances inward, the dust is also pushed by the screw and falls into the car stereo body.
Japanese Utility Model Application Laid-Open 64-385 discloses a structure for mounting a transistor on a board where the transistor is secured by a screw engaged in a threaded hole though a hole formed in insulating sheet adhered on the board. The size of the hole is slightly smaller than the threaded hole, so that the transistor is separated from the screw, and hence protected from the metal chips.
Japanese Utility Model Application Laid-Open 1-166811 discloses a rubber bush enclosing a screw for preventing the metal chips from dispersing. However, these structures are provided for preventing the metal chips of the screw from falling to the outside of the instrument. Therefore, the prior art does not effect to prevent the chips from entering the electric instrument through the screw hole.